Patrik Rogalla

Isotropic half-millimeter angiography of coronary artery bypass grafts with 16-slice computed tomography.

BACKGROUNDnComputed tomography (CT) with four detector rows and magnetic resonance imaging (MRI) are still of limited value for the assessment of coronary artery bypass grafts (CABG). We investigated the abilities of 16-slice CT in these patients.nnnMETHODSnA retrospective analysis of all noninvasive coronary angiographies with multislice computed tomography (MSCT; Aquilion, Toshiba) on patients with CABG referred to our institution between October 2002 and April 2003 was conducted. MSCT angiography was performed using a standard protocol (0.5-seconds rotation time, 16 x 0.5 mm detector collimation, 120 kV, 250 to 300 mA, and 0.25 pitch). None of the patients received beta-blockers to reduce the heart rate. Seventy-five CABGs (20 arterial grafts and 55 venous grafts) in 27 patients were evaluated for patency and adequate diagnostic quality by two radiologists in consensus.nnnRESULTSnAll arterial and venous grafts were depicted with adequate diagnostic quality and were eligible for evaluation. Fifteen occlusions and five significant stenoses (at least 50%) could be identified. All of the proximal and 99% of the distal anastomoses were eligible. One distal anastomosis of an arterial graft was not assessable due to surgical clip artifacts. The length of the acquisition window was 174 +/- 46 ms (range 71 to 234 ms). The majority of the patients (70%) had a heart rate above 65 beats/min. However, due to the improved temporal and spatial resolution none of the examinations had an insufficient image quality.nnnCONCLUSIONSnMSCT angiography with 16 detector rows and an isotropic high resolution reliably depicts CABG with adequate diagnostic quality.

Virtual endoscopy and related 3D techniques

Technical Background (J.Terwisscha van Scheltinga).- Virtual Endoscopy of the Nose and Paranasal Sinuses (P. Rogalla).- Virtual Laryngoscopy (A.J. Aschoff/E.M. Merkle).- Virtual Endoscopy of the Trachea and Bronchi (P. Rogalla/N. Meiri).- Virtual Endoscopy of the Small Intestine (P. Rogalla).- Virtual Endoscopy of the Colon (P. Rogalla/N. Meiri/C.I. Bartram).- The Investigation (P. Rogalla/N. Meiri).- A Historical and Clinical Perspective (C.I. Bartram).- Virtual Cystoscopy (T. Fleiter/E.M. Merkle/C. Wisianowsky).-Virtual Endoscopy of the Vessels (T.H. Wiese/P. Rogalla).- Virtual Neuroscopy (S. Gottschalk).- Virtual Otoscopy (R. Klingebiel).- Subject Index.- List of Contributors.

A Method for Adjusting a Malpositioned Bifurcated Aortic Endograft

Purpose: To report the successful application of a method to adjust a malpositioned bifurcated stent-graft after endovascular aortic aneurysm repair. Method and Results: A 62-year-old male patient underwent endovascular repair of a 5.1-cm abdominal aortic aneurysm (AAA) with a Vanguard bifurcated stent-graft. After complete deployment of the stent-graft, the intraoperative completion angiogram disclosed unexpected occlusion of the left renal artery. Intra-aortic adjustment of the bifurcated graft was possible with a crossover guidewire, which was pulled caudally. The method worked perfectly to restore blood flow to the left renal artery. The patient is well 16 months postoperatively without any evidence of endoleak or graft migration; the left renal artery remains open. Conclusions: A technique is demonstrated for intra-aortic repositioning of a bifurcated stent-graft to correct insufficient deployment. If required, this technique should be attempted before conversion to an open procedure.

Unsupervised extraction and quantification of the bronchial tree on ultra-low-dose vs. standard-dose CT

Automatic extraction of the tracheobronchial tree from high resolution CT data serves visual inspection by virtual endoscopy as well as computer aided measurement of clinical parameters along the airways. The purpose of this study is to show the feasibility of automatic extraction (segmentation) of the airway tree even in ultra-low-dose CT data (5-10 mAs), and to compare the performance of the airway extraction between ultra-low-dose and standard-dose (70-100 mAs) CT data. A direct performance comparison (instead of a mere simulation) was possible since for each patient both an ultra-low-dose and a standard-dose CT scan were acquired within the same examination session. The data sets were recorded with a multi-slice CT scanner at the Charite university hospital Berlin with 1 mm slice thickness. An automated tree extraction algorithm was applied to both the ultra-low-dose and the standard-dose CT data. No dose-specific parameter-tuning or image pre-processing was used. For performance comparison, the total length of all visually verified centerlines of each tree was accumulated for all airways beyond the tracheal carina. Correlation of the extracted total airway length for ultra-low-dose versus standard-dose for each patient showed that on average in the ultra-low-dose images 84% of the length of the standard-dose images was retrieved.

Comparative performance analysis for computer aided lung nodule detection and segmentation on ultra-low-dose vs. standard-dose CT

The performance of computer aided lung nodule detection (CAD) and computer aided nodule volumetry is compared between standard-dose (70-100 mAs) and ultra-low-dose CT images (5-10 mAs). A direct quantitative performance comparison was possible, since for each patient both an ultra-low-dose and a standard-dose CT scan were acquired within the same examination session. The data sets were recorded with a multi-slice CT scanner at the Charite university hospital Berlin with 1 mm slice thickness. Our computer aided nodule detection and segmentation algorithms were deployed on both ultra-low-dose and standard-dose CT data without any dose-specific fine-tuning or preprocessing. As a reference standard 292 nodules from 20 patients were visually identified, each nodule both in ultra-low-dose and standard-dose data sets. The CAD performance was analyzed by virtue of multiple FROC curves for different lower thresholds of the nodule diameter. For nodules with a volume-equivalent diameter equal or larger than 4 mm (149 nodules pairs), we observed a detection rate of 88% at a median false positive rate of 2 per patient in standard-dose images, and 86% detection rate in ultra-low-dose images, also at 2 FPs per patient. Including even smaller nodules equal or larger than 2 mm (272 nodules pairs), we observed a detection rate of 86% in standard-dose images, and 84% detection rate in ultra-low-dose images, both at a rate of 5 FPs per patient. Moreover, we observed a correlation of 94% between the volume-equivalent nodule diameter as automatically measured on ultra-low-dose versus on standard-dose images, indicating that ultra-low-dose CT is also feasible for growth-rate assessment in follow-up examinations. The comparable performance of lung nodule CAD in ultra-low-dose and standard-dose images is of particular interest with respect to lung cancer screening of asymptomatic patients.

Popliteal artery occlusion as a late complication of liquid acrylate embolization for cerebral vascular malformation

Occlusion of arteriovenous malformations of the brain (BAVMs) by means of an endovascular approach with liquid acrylate glue is an established treatment modality. The specific hazards of this procedure are related to the central nervous system. In the case of unexpectedly rapid polymerization of the cyanoacrylate glue and adhesion of the delivering microcatheter to the BAVM, severing the catheter at the site of vascular access is considered an acceptable and safe management. We present a unique complication related to this technique that has not been described yet. Fragmentation and migration of the microcatheter, originally left in place, had caused popliteal artery occlusion, which required saphenous vein interposition, in a 25-year-old man. Suggestions for avoiding this complication are discussed.

Multiple Thrombosis With Aortic Occlusion After Heparin-Induced Thrombocytopenia Demonstrated by Multislice Computed Tomography

A 41-year-old woman with restrictive cardiomyopathy due to amyloidosis underwent insertion of an automatic implantable cardioverter-defibrillator for treatment of ventricular tachyarrhythmia. Unfractionated heparin was given as an anticoagulation agent.nnSixteen days after the procedure, the patient had abdominal and leg pain, development of paresis of the lower extremities, and both urinal and fecal incontinence. A subsequently performed contrast-enhanced multislice CT demonstrated thrombi in both the left and right atrial appendage and at different levels of the thoracic and abdominal aorta extending into both …

Combined surgical and endovascular removal of thrombus entirely occluding a bifurcated aortic stent-graft.

Purpose: To explore a method combining interventional, endovascular, and conventional surgical techniques for treating a completely occluded bifurcated stent-graft after endovascular aortic aneurysm repair. Methods and Results: A 60-year-old patient underwent endovascular repair of an abdominal aortic aneurysm (AAA) with a Talent bifurcated stent-graft. Five months later, after chronic thrombotic occlusion of the right iliac limb, he presented with acute occlusion of the entire stent-graft. Local intra-arterial infiltration thrombolysis successfully reconstituted flow through the main aortic segment and left iliac limb. With a combination of conventional surgical and intraoperative endovascular procedures, thrombectomy and recanalization of the right iliac limb was completed by stenting a severe stenosis of the proximal iliac limb. Conclusions: A combination of techniques may be essential for successful management of thrombotic complications after endovascular AAA repair.